Chlamydial polyarthritis-enteritis results from damage to intestinal, synovial, conjunctival and other specialized cell types induced by uniquely pathogenic strains of Chlamydia psittaci. Investigations of properties of these enteropathogenic and arthropathogenic chlamydiae and their interaction with different cultured cells and cells in tissues of infected animal hosts will elucidate mechanisms of cell damage and pathogenesis. The overall objectives are: 1. To identify properties of immunotype 1 and 2 strains of C. psittaci of animal origin through analysis of antigens, immediate toxic potential, and interaction with cultured cells. 2. To compare their response to procedures enhancing uptake by host cells, to analyze infectivity yields and to characterize minicell development and other aberrant chlamydial forms in low yield infections. 3. To assess the role of lysosomes in chlamydial infections of cells in synovial tissues and in the gradient of cells differentiating on intestinal crypts and villi. 4. To define the host cell range infected in synovial membranes in arthritis induction and to relate changes in cellular organelles to stages of chlamydial development. 5. To explore the phenomenon of chlamydial immediate toxicity for cells in the dynamics of mucous membrane infections. Using electron microscopic, ultrastructural cytochemical, enzymatic, immunologic, and cell fractionation methods, the effect of chlamydial infection in cellular organelles will be explored. Animals will be inoculated to study sequential changes in the induction of enteritis and arthritis, and other phases will be explored in organ or cell culture systems.